Bio-CO2: Power Generation and Heat Recovery from Biomass with Advanced CO2 Thermodynamic Power Cycles and Novel Heat Exchanger Designs

在英国，发电主要是通过燃烧来自偏远发电站的化石燃料实现的，效率低至40%。这会导致能源的大量消耗和环境污染。实际上，在考虑到远距离输电和配电损耗后，发电效率往往会进一步降低到供电端的32%左右。为了解决这个问题，可以使用本地和分散的热电联产（CHP）系统，不仅可以达到30%的电效率，还可以达到50%以上的热效率，这将显着提高能源利用率。在同时需要供暖和电力的地区，包括超市和地区供暖，这种系统将是一种可行的经济选择。然而，目前大多数热电联产系统仍然需要化石燃料能源，这降低了它们的节能优点和潜在的CO2减排。因此，通过优化的热电联产系统工程设计来促进本地化可再生资源（如生物质燃料）的使用将是非常可取的。目前，主要有两种生物质热电联产系统：利用燃气/蒸汽涡轮机的生物质气化和利用有机兰金循环（ORC）的生物质燃烧。然而，在解决某些关键问题之前，这些生物质热电联产系统不能进一步发展或广泛应用。这些包括实现可接受的热效率、紧凑的系统尺寸、环境友好的工作流体、先进的热力学动力循环、优化的系统设计和控制以及灵活的操作等。另一方面，对于中高温热源的发电，CO2超临界布雷顿循环（S-CO2）可以在热效率方面优于传统的ORC，环境影响和系统紧凑性。S-CO2系统已应用于核电站的大规模余热回收，但由于各种尚未解决的挑战，尚未用于生物质发电。在这个拟议的项目中，一个小规模的生物质发电系统与先进的二氧化碳超临界布雷顿循环和新的换热器设计将进行实验和理论研究。该研究将解决所提出的系统中涉及的挑战，包括热驱动CO2超临界压缩机的创新设计，S-CO2压缩机入口处的精确CO2参数控制，超临界CO2热交换器的新颖设计以及对所涉及的复杂传热和液压过程的全面理解。此外，将开发生物质S-CO2发电系统的详细瞬态模型，这将使系统能够进一步优化和扩大实际设计和操作。

In the UK, power generation is achieved mostly through the combustion of fossil fuels from remote power stations at a low-efficiency rate of 40%. This can lead to a large depletion of energy resources and pollution to environment. In reality, after taking into consideration long-distance power transmission and distribution losses, the generation efficiency tends to be further reduced to around 32% at the power supply end. To combat this problem, a local and decentralised combined heat and power (CHP) system may be used to attain not only 30% electrical efficiency but also over 50% heating efficiency, which would significantly improve the energy utilisation rate. In areas with simultaneous heating and electricity demand including supermarket and district heating, such systems would be a viable economic option. However, currently most CHP systems still require fossil fuel energy resources, which diminish both their energy-saving merit and potential CO2 emission reductions. Therefore, it would be highly desirable to promote the use of localised renewable resources, such as biomass fuels, with optimised CHP system engineering designs.Currently, there are two main biomass CHP systems: biomass gasification with gas/steam turbines and biomass combustion with Organic Rankin Cycles (ORC). However, these biomass CHP systems cannot be further developed or extensively applied before the resolution of certain critical issues. These include achieving an acceptable thermal efficiency, compact system size, environmentally-friendly working fluid, advanced thermodynamic power cycles, optimal system design and control, and flexible operation etc. On the other hand, for power generation with medium to high temperature heat sources, CO2 supercritical Brayton cycles (S-CO2) can predominate over conventional ORCs in terms of thermal efficiency, environmental impact and system compactness. The S-CO2 systems have been applied in large-scale waste heat recovery of nuclear power plants but have not yet been utilised in biomass power generations due to various unsettled challenges. In this proposed project, a small-scale biomass power generation system with advanced CO2 supercritical Brayton cycles and novel heat exchanger designs will be investigated experimentally and theoretically. The investigation will address the challenges involved in the proposed system including innovative designs of thermal drive CO2 supercritical compressors, precise CO2 parameter controls at the S-CO2 compressor inlet, novel designs of supercritical CO2 heat exchangers and comprehensive understanding of the complex heat transfer and hydraulic processes involved. In addition, a detailed transient model of the biomass S-CO2 power generation system will be developed which will enable the system to be further optimised and scaled up for actual design and operation.